Nielsen



1956 F. NIELSEN 2,735,147

' GATING SYSTEM FOR CASTING METALS Filed Jan. 9, 1953 2 Sheets-Sheet 1IN VENTOR Friedrich Nielsen Feb. 21, 1956 F. NIELSEN 2,735,147

GATING SYSTEM FOR CASTING METALS Filed Jan. 9, 1953 2 Sheets-Sheet 2RATIO ANGLE INVENTOR F 9 Friedrich Melee/2 United States Patent GATINGSYSTEM FOR CASTING METALS Friedrich Nielsen, Muhlacker, GermanyApplication January 9, 1953, Serial No. 330,479

Claims priority, application Germany October 31, 1949 3 Claims. (Cl.22-134) This invention relates to the casting of metals. In

particular, the invention is directed to a gating system for pouringmolten metal, especially light metals, into a mold.

This invention is a continuation-in-part of my application S. N.261,956, filed December 17, 1951, for Casting Metals, now abandoned.

In recent years the art of pouring molten metals has been increasinglyinterested in the technique of the socalled gating practice in which themolten metal is poured from a ladle into a pouring runner from which itflows through a gate into a mold. Heretofore the design of the systemhas most frequently been based on the.cross-sec tional ratio between therunner inlet, the runner, and the gate outlet from the runner, as forexample 4:322, or 102915, or 100:95290, or 3.6:4:2. These numericalproportions merely approximate the dimensions of a pouring runner inwhich the cross-section is narrowed from the inlet to the outlet gate sothat the velocity of flow of the molten metal is not sensibly impeded bythe runner. Whatever advantages which may be obtained from such systemare offset by the fact that the velocity of the metal entering the moldcreates eddys and flow shocks in the casting which are very detrimentalto the same.

In order to avoid disturbances of the metal in the mold, it has beenproposed to slow the velocity of the metal in a straight runner byprogressively, in steps, widening the way from the inlet through therunner to the gates as for example in the ratio of 1:25:10. However,although the principle of diminished velocity to produce laminar flow atthe gate is met, in actual practice the runner became so wide adjacentthe gate as to permit the formation of slag and oxide skins on the verylarge exposed surface of the slowly flowing molten metal. In addition, auniform flow cannot be maintained at the gate in the beginning of thecasting as the molten metal does not entirely fill the wide runneradjacent the gate.

The objects of this invention are to produce a casting system in whichboth the exposed surface area of the molten metal and the velocity ofdischarge into the mold are kept to a practical minimum; to produce arunner in which the kinetic energy of the molten metal received from aladle is dissipated substantially before the metal is discharged throughthe gate; and to produce a runner by means of which a steady,quasi-laminar flow of metal into a mold is obtained.

In general, these objects are obtained by constructing a covered runnerhaving a plurality of straight sections connected to each other by sharpbends and which widens from the inlet to the outlet gate. Preferably therunner has right angle turns so that as the metal flows around each turnthere is an impact loss of energy and a corresponding decrease invelocity. Each successive section between bends is proportionatelyincreased in-width and cross-sectional area so that a uniform volume offlow is maintained through the runner. Consequently, the molten metalcan be' discharged from the runner at a velocity which will not causedisturbances in the mold, T

and at the same time the'cross-section of the runner is kept smallenough so that the surface of the metal will not oxidize to anobjectionable extent.

The invention is described more fully with reference to the accompanyingdrawings in which the invention is illustrated diagrammatically.

Figure 1 is a front view of a runner system according to the invention,a portion being shown in section on the line 11, Fig. 2;

Figure 2 is a plan view of the invention shown in Fig. 1;

Figure 3 is a front view of a modified form of the invention, partlyshown in section on the line 3-3, Fig. 4;

Figure 4 is a plan view of the invention shown in Fig. 3;

Figure 5 is a front view of a third form of the invention, shown partlyin section on the line 5-5, Fig. 6;

Figure 6 is a plan view of the invention shown in Fig. 5;

Figure 7 is a front view of a fourth form of the invention;

Figure 8 is a cross-sectional view on the line 8-8, Fig. 7; and

Figure 9 is a graph showing the range in which the invention can bepracticed.

In Figures 1 to 8, the invention is described for a gating system inwhich the runner sections are connected at angles. For other angles theratios are shown in Figure 9.

As seen in Figs. 1 and 2, the runner 10 is provided with an inlet 12through which molten metal is received from a furnace, or ladle, andwith outlet gates 14 through which metal flows into a mold 16.

Runner 10 has a course including sharp abrupt bends between the inletand the gates. Channel section 16, ad jacent inlet 12, is narrow and isjoined to section 18 of greater width by a right angle turn. Section 18similarly joins section 20, which likewise is continued into section 22and gates 14. In the diagrammatic drawings the slope of the channel andthe slight rounding of the corners according to conventional practiceare omitted.

Molten metal enters the runner through inlet 12 with a velocitydetermined by the height of metal in the inlet. The flow of molten metalon being deflected into section 18 suffers an energy loss, and as theflow of metal is briefly and successively deflected into channels 20 and22, and out through gates 14 the velocity of flow is diminished further.

In deflecting the flow of metal through an angle of 90, the impactenergy loss causes about a 37.5% reduction in velocity, the flow intothe succeeding channel amounting to 62.5% of the original velocity.Consequently, in order to maintain a uniform volume of flow, the newchannel section must have a cross section increased about or 1.60 timesthe cross-section area of the first channel section. Thus, channelsection 18 has a cross-sectional area 1.6 times that of channel 16, andsections 20, 22 and gates 14, respectively each increased over thepreceding section. Each section need only be long enough to obtain thedesired deflection and energy loss, and each section has a length asshort as permitted by runner construction, a length of a few centimetersusually being sufflcient. The inner corners of the channel may beslightly rounded in order to maintain good flow characteristics, but theouter corners should be kept as sharp as possible in order to gain themaximum impact energy loss.

It is practical to work with smaller ratios for the stages of wideningthe channel sections, as for example 3:4=1.33, which corresponds toabout a 25% velocity reduction ineach stage. Any residual small staticexcess Channel Section Cross-sectional area (sq. mm.) 100 141 200 283400 Pressure Head (cm.) 32 16 8 4 2 Velocitycm.isec 250 177 125 88 62. 5

The cross-sectional area given for gates 14 represents the combinedareas of the several gates.

it can be seen from the above table that the static pressure head at thegates is only in the order of a few centimeters, and this head will notincrease as pouring takes place. A calm filling of the mold is thusensured throughout the pouring operation.

While in Figures 1 and 2 the channel sections are shown of equal height,but of varying width, the height can be also varied as shown in Figures3 and 4, this sometimes being desirable in order that the runner can beadapted to the shape of a mold and the position of the gates withrespect thereto. In Figures 3 and 4, from inlet 30, channel sections 32,34, 36 and 38 are of progressively decreasing height, and increasingwidth, including gate 40, from which metal is discharged into mold 42.Furthermore, the loss of energy impact effect is increased by extendingeach channel section slightly beyond the connection with the succeedingsection as shown at 33, 35, 37 and 39.

Special provision can be made for the collection of slag or oxideformations as shown in Figures 5 and 6. From inlet 50, channel sections52, 5 4, and 56 as well as gates 60 are designed as described for Figure1, metal flowing to mold 62. One or more channel sections can be formedas a slag collector, preferably the next to the last stage as section58. This section is higher than the preceding sections so that the slagfloating on top of the molten stream will collect. Normally, thecross-sectional area of the collecting section should be in conformitywith its place in the sequence of sections. It may be larger if thepreceding and succeeding sections are in proper ratio, for example, as1:2 when the step ratio is 1:1.41; or 1:1.77 if the ratio is 3:4. Insuch enlarged sections, additional energy losses may occur due todirection changes and impact losses, and such must be allowed for in thedesign of the entire system.

In Figures 7 and 8, the system is applied to the casting of verticalmolds, and also illustrates the use of branched channel sections. Moltenmetal flows vertically downward in inlet 70, then horizontally throughchannel section 72, then vertically through section 74. The channel isthen split into branches 76a and 76b, the combined area of which equalsthe value necessary to maintain the sequential ratio adopted for thesystem. Branches 76:: and 76b serve as distribution'channels servinggates 80 from which metal is discharged into molds 82. Where more thanone gate exists for one branch, as shown, the channel branch section isnarrowed, as at 77a and 77b, adjacent the outermost gate in order tomaintain equal fluid pressures at all the gates.

The-system of Figures 7 and 8 ensures the correct feeding of metal to aplurality of similar molds, or to various inlets into a large casting,with a reliability greater than heretofore obtainable. Unequal feedingthrough a plurality of gates is virtually eliminated.

Branched section channels can also be used in the horizontal castingsystems of Figures 1 to 6. The sections may be branched, andsubsequently united without the risk of causing the metal to eddy orfroth if done when the metal has reached a low velocity section.

If, in a vertical casting, the mold is so large as to require the use oflateral gates, the sum of all the gate areas may exceed the establishedratio because the gates come into operation one after the other. Thusthe last distribution channel can be increased beyond the ratio as thelow velocity has already been achieved in the preceding channelsections. In the case of very large molds, the use of lateral gates isto be recommended in view of the low rising speed ofthe mteal. Even inhorizontal castings it is sometimes advantageous to have the channelsections gently sloped upwards toward the gates when a particularly lowdischarge speed is desired.

In Figure 9, the graph illustrates the range of angles and ratios inwhich the invention can be practiced. The limits for an angle of 20 areratios from 1.05 and 1.2. The limits for an angle of 150 are ratios from1.3 and 2.5. The upper curve AB and the lower curve CD define the areawithin which the system successfully operates. Above the curve AB, theratios produce a system in which foaming occurs in the runner system,while below curve CD, the ratios produce eddy currents and slag in themold. Preferably, in the ordinary case, the ratios employed are those inthe area lying in the upper half of the middle third between curves ABand CD.

The simplest system is to have 90 connections between the runnersections. However, it is desirable at times to use other angles, orcombinations of other angles in the system. This is determined by theway the mold is situated, the shape of the casting and other factors.For example, where very high inlets are used, it is desirable to useangles less than 90 in the beginning of the system because the reactionpressures on the walls of the runner are small, and the runner sectionsare saved from wear. In generahthe energy losses increase as the anglesincrease. Where combinations of angles are used, the ratio of increasein cross-section permissible in the system can be selected from Figure9.

The principles of the invention are also applicable to the normal pouredcasting where the metal is simply poured into the top of a mold, and topressure casting, as the maintenance of a smooth quasi-laminar flow ofmetal devoid of gas, bubbles, and eddy disturbances, in-

herently produces a superior casting.

Having now described the means by which the objects of the invention areobtained, I claim: 7

1. In a gating system, a molten metal pouring runner having an inlet endand a discharge gate, further comprising communicating channel sectionsjoined to each other and forming a runner having a plurality of anglesto effect a loss in kinetic energy in metal flowing through saidsections to said discharge gate, each channel section between said inletend and said discharge gate being successively increased incross-section in a ratio lying between the curves AB and CD in Figure 9of the drawings.

2. In a gating system as in claim 1, the height of said channel sectionsbeing progressively decreased from said inlet end to said dischargegate.

3. In a gating system as in claim 1, one of said'sections being branchedwith the sum of the cross-sectional areas of the branches being equal tothe cross-sectional area required for the sequential position of saidbranched section in said runner system.

References Cited in the file of this patent UNITED STATES PATENTS1,553,628 Norton Sept. 15, 1925 2,219,012 Kirby Oct. 22, 1940 2,629,647Arnette Nov. 14, 1950 OTHER REFERENCES

1. IN A GATING SYSTEM, A MOLTEN METAL POURING RUNNER HAVING AN INLET ENDAND A DISCHARGE GATE, FURTHER COMPRISING COMMUNICATING CHANNEL SECTIONSJOINED TO EACH OTHER AND FORMING A RUNNER HAVING A PLURALITY OF ANGLESTO EFFECT A LOSS KINETIC ENERGY IN METAL FLOWING THROUGH SAID SECTIONSTO SAID DISCHARGE GATE, EACH CHANNEL SECTION BETWEEN SAID INLET END ANDSAID DISCHARGE GATE BEING SUCCESSIVELY INCREASED IN CROSS-SECTION IN ARATIO LYING BETWEEN THE CURVES AB AND CD IN FIGURE 9 OF THE DRAWINGS.